Changes in Drip Irrigation Water Distribution Patterns Improve Fruit Quality and Economic Water Productivity in Early-Season Lemon Trees

The physiological and agronomic responses of two irrigation systems were compared in 'Fino 49 & PRIME; lemon trees (Citrus limon [L.] Burm. fil.). The irrigation systems consisted of different designs of the irrigation installation (same amount of water and irrigation frequency): a conventional design (2L, two drip lines with six drippers per tree), and a design with a larger wetted surface (3L, implementing the conventional design with a third drip line with nine drippers per tree). Results indicated that the 3L design promoted a better distribution of water and fertilisers in the soil profile, improving some gas-exchange parameters in periods of low evaporative demand or after rain. The agronomic response showed two main effects on fruit quality: (1) the total numer of fruits affected by endoxerosis was reduced, and (2) the first harvest (the earliest fruits harvested) moved forward in time. From an economic point of view, economic water productivity was increased, mainly due to an increment in the proportion of first-harvested lemon, but also due to the decrease in lemon produced for the industry (affected by endoxerosis). The 3L irrigation system could be an interesting alternative to favour fruit precocity, improving the use of the available water resources for early lemon tree growers.